Earthquake · reviewed by a seismologist
M 1.9ml
Earthquake near Polson, MT
USGS: 18 km SSE of Swan Lake, Montana
- When
- 1:04 am MST on 21 November 2019 ()
- Where
- 34 km (21 mi) ENE of Polson, MT · earthquakes near Polson
- Magnitude
- M 1.9 (ml)
- Depth
- 6.6 km below the surface
- Felt
- no reports yet
- Nearest
- Lake County, 31 km WSW
- Nearest mapped fault
- Mission fault, 20 km from its surface trace — near is not the same as on
- Status
- Reviewed by a seismologist
USGS · last changed by USGS · we first saw it 2507 days ago
A magnitude 1.9 earthquake was recorded 34 km (21 mi) ENE of Polson, MT, at 1:04 am MST on 21 November 2019 (08:04 UTC). This was a minor earthquake. Quakes this small are rarely felt and do not cause damage.
How big was it?
This earthquake released about 20 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.9 would have released about 32 times as much.
- Mineral, Virginia 2011 M 5.8 760,000× the energy of this one
- Magna, Utah 2020 M 5.7 540,000× the energy of this one
- Around the size people start to feel M 3.0 48× the energy of this one
- This earthquake M 1.9 about 20 lb of TNT
Energy from the Gutenberg–Richter relation (log10E = 1.5M + 4.8), rounded to two figures; bar length is magnitude, which is already a logarithm of energy. Magnitudes of past earthquakes from the USGS catalogue.
For this area
No earthquake of M4 or more has been recorded within 50 km since our catalogue begins in 2016.
Before 2016, the USGS record lists one earthquake of M5 or more within 50 km:
- 5.5 Western Montana · 24 km NNW of this epicentre
Since 2016: the QuakeIndex catalogue (US, M1.5+), built from the USGS FDSN event service. Before 2016: USGS ComCat, M5+ from 1900. Distances are between epicentres. This is the record, not a forecast.
Where
Epicentre 47.7870, -113.7270. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Lake County, MT | 31 km (19 mi) | WSW | earthquakes near Lake County |
| Flathead County, MT | 61 km (38 mi) | NNW | earthquakes near Flathead County |
| Missoula County, MT | 85 km (53 mi) | S | earthquakes near Missoula County |
| Teton County, MT | 108 km (67 mi) | E | earthquakes near Teton County |
| Sanders County, MT | 109 km (68 mi) | W | earthquakes near Sanders County |
| Glacier County, MT | 116 km (72 mi) | NNE | earthquakes near Glacier County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
55 earthquakes have been recorded within 50 km since this one.
- 2.1 27 km E of Swan Lake, Montana
- 2.5 24 km E of Swan Lake, Montana
- 2.4 27 km E of Swan Lake, Montana
- 2.3 10 km NNW of Swan Lake, Montana
- 1.7 15 km NNE of Bigfork, Montana
- 2.0 40 km E of Condon, Montana
- 3.0 17 km SSE of Swan Lake, Montana
- 1.6 9 km ENE of Ronan, Montana
- 1.5 6 km SW of Condon, Montana
- 1.7 5 km ESE of Lakeside, Montana
- 1.6 15 km ESE of Condon, Montana
- 1.5 8 km ESE of Woods Bay, Montana
- 2.1 18 km SSE of Swan Lake, Montana
- 1.8 17 km SSW of Condon, Montana
- 1.9 17 km SSW of Condon, Montana
Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of . QuakeIndex does not forecast aftershocks. When USGS issues an operational aftershock forecast it appears on the USGS event page.
On USGS
- The official USGS event page — the source of record for every value above
- Did you feel it? Report it to USGS — reports go to USGS, not to us
- ShakeMap for this event, when USGS has produced one
QuakeIndex does not issue warnings. For earthquake early warning see ShakeAlert.